In the related art, as an electronic control unit (an electronic unit) for controlling various types of electrical components to be mounted on a vehicle, for example, the one described in Patent Document 1 is known. Commencing with the electronic control unit described in Patent Document 1, the electronic control unit of this type generally includes a substrate on which a connector for external connection is mounted, and a case configured to accommodate the substrate. The case includes a case body configured to accommodate the substrate and a cover member to be mounted on the case body. The substrate is fixed to the case body with screws, or fixed to the case body, for example, by being press-fitted to the inside of plural ribs formed on the case body, and is accommodated in the case from an opening or the like formed on the cover member in a state in which the connector is exposed to the outside.
The electronic control unit is assembled to a J/B (Junction Box: electric connection box), and is assembled to a vehicle in a state in which the connector and a connector on the J/B side are directly connected in many cases. In contrast, details of control of the electronic control units are different depending on the grades of the vehicle or selected options, so that different types of substrates are required to be mounted correspondingly. In this case, when mounting of the substrates different in size is required, plural types of cases different in internal shape such as screw holes for fixing the substrate or positions of ribs from each other while being common in outline shape (the size and the shape) are prepared, and these cases are selectively used in accordance with the sizes of the substrates.
However, when selectively using plural types of specific cases as described above, plural dies are required for molding the cases, which is disadvantageous in terms of manufactures' costs. Also, it is required to manage plural types of cases common in outline shape of the cases, and hence component management is complicated. In addition, when plural different types of cases are mixed, the assembly work of the electronic control unit may be affected.